How the Laughing Cavalier keeps an eye on everybody

From second-rate horror films to episodes of Scooby-Doo, ominous paintings whose staring eyes follow a character around the room, no matter where they go, have been used to spooky effect. But now a team of scientists believe they have solved the mystery of how they do it.

A group working on how our brains interpret images found that as long as a character in a painting is looking straight ahead, our brains will perceive they are staring at us, no matter the angle from which we view the painting. A striking example is The Laughing Cavalier by Frans Hals, the 17th century Dutch painter.

The explanation lies in how we interpret three-dimensional objects portrayed on a flat surface. Real three-dimensional objects look different depending on the angle bec-ause of the changing way light falls across them. But on the flat canvas, shading and light are fixed and the image looks the same from every angle.

James Todd of Ohio State University and co-author of the study said: "If a person in a painting is looking straight out, it will always appear that way, regardless of the angle at which it is viewed."

The scientists, writing in the journal Perception, took hundreds of measurements of 3D images displayed on a computer screen. They found that whatever angle the images were viewed from, they always looked the same.

Jonathan Jones, the Guardian's art critic, said: "It'd be wonderful if people gave art historians the kind of grants that scientists seem to get to research art."